Verses with the word marah in the Old Testament (3 verses):

Exodus 15:23
And when they came to Marah, they could not drink of the waters of Marah, for they were bitter: therefore the name of it was called Marah.

Numbers 33:8
And they departed from before Pihahiroth, and passed through the midst of the sea into the wilderness, and went three days' journey in the wilderness of Etham, and pitched in Marah.

Numbers 33:9
And they removed from Marah, and came unto Elim: and in Elim were twelve fountains of water, and threescore and ten palm trees; and they pitched there.